The PWM ripple compensation makes the filter a 2nd order filter. It can still be worth it as it is a relatively simple way to build a 2nd order filter, but no magic.
For combining 2 PWM channels for extra high resolution it helps if the fine part is really only a small fraction, as the resistor (and switch resistance) accuracy limits the useful resolution for the fine part to some 5-8 bits. So for 16 bit total one would not use 8 + 8 bits with a 1:258 resistor ratio, but more like 12+4 bits.